Section A provides a review of empirical literature researching therapists’ experiences, opinions and attitudes towards the practice of model fidelity. Sixteen studies are reviewed, synthesized and critiqued, and findings are categorised into themes. Results of the review suggest therapists have complex relationships with model fidelity, shaped by multifaceted combinations of attitudes, values, personal, professional and skill development, clinical complexity, and experience. Findings are also considered in relation to pertinent theories. Clinical and research implications are discussed. Section B presents a grounded theory of model fidelity in clinical psychologists’ therapeutic practice. The theory was developed from semi-structured interviews conducted with 13 clinical psychologists with varying expertise. Through analysis, a hierarchy of categories emerged from the data, describing stages of therapeutic practice. The grounded theory suggests that clinical psychologists have evolving relationships with model fidelity, moving from model-centred practice to person-centred approaches with greater experience. Implications for clinical practice and research are discussed.